(1) Field of the Invention
The present invention relates to a backlight for a liquid crystal display device and a liquid crystal display device using the same, and in particular, to a backlight for a liquid crystal display device where a number of point light source elements are regularly aligned in a plane and a liquid crystal display device using the same.
(2) Related Art Statement
Conventional liquid crystal display devices use a backlight for illuminating the liquid crystal panel from the rear. Various types of light sources can be used as the backlight, and fluorescent lamps, such as cold cathode tubes and external electrode fluorescent lamps, surface light sources, such as electroluminescence, and point light sources, such as light emitting diodes, are mainly used.
In recent years, demands in an increase in the size of the screen of liquid crystal display devices, a reduction in the power consumption and control of the turning on and off of the backlight in accordance with the displayed image have specifically made the need for a backlight where light emitting diodes are arranged in a plane.
As shown in FIGS. 1A and 1B, light emitting diodes (LED's) 2, which are point light source elements, are regularly aligned in a plane on a support substrate 3, and thus, form a backlight 1 for a liquid crystal display device. FIG. 1A is a plan diagram showing the backlight, and FIG. 1B is a cross sectional diagram along arrows X-X′ in FIG. 1A.
In addition, a reflective sheet 4 where openings 40 are created in positions where LED's are provided is placed on the support substrate 3. This works to direct light emitted from the LED's in the direction towards the liquid crystal panel provided in front of the backlight.
Such a backlight is disclosed in JP2007-73295A, and the structure where a backlight is formed of a single support substrate causes the cost for manufacture to increase as the size of the screen of liquid crystal display devices increases. That is to say, a single support substrate corresponding to a large screen has a high cost and is difficult to handle, and it is necessary to replace the entirety of the substrate even in the case where there is a defect in a portion of a region of the support substrate, which ends up being an extremely high cost.
In order to solve these problems, as shown in FIG. 2, the entire region A where point light source elements 2 are aligned is divided into a number of smaller regions a1 to a8 so that support substrates 31 to 38 are provided for respective smaller regions, and LED's 2, which are point light source elements, are arranged on the respective support substrates. The symbols 51 to 58 are connectors for supplying power in order to drive the LED's 2 arranged on the respective support substrates. Here, dotted lines in FIG. 2 simply indicate that the LED's 2 are aligned side-by-side.
Support substrates having a relatively small size can be used as these divided support substrates, and when there is a defect in a portion of the region of the backlight, only the corresponding support substrate is replaced so that the backlight can be easily repaired. In addition, as shown in FIG. 2, the same backlight units having the same number and the same arrangement of LED's can be used for the respective smaller regions a1 to a8 in the case where the entire region A is divided equally into support substrates having the same size, and thus, it is possible to greatly reduce the cost for manufacture.
In addition, the reflective sheet 4 shown in FIGS. 1A and 1B can be used in the same manner for the divided support substrates.